/Engine/Source/Runtime/Engine/Classes/Kismet/KismetMathLibrary.h
Returns a random vector with length of 1, within the specified cone, with uniform random distribution.
static FVector RandomUnitVectorInConeInRadiansFromStream ( const [FRandomStream](API\Runtime\Core\Math\FRandomStream) & Stream, const FVector & ConeDir, float ConeHalfAngleInRadians )